Schoolchildren who witness violence, shootouts or hear gunshots is traumatised by them, a new study confirms.
Young people living in US cities experience and witness high levels of serious and lethal violence, which leaves lasting negative effects on their health.
Although the mechanisms are yet to be confirmed, one plausible explanation is that the body's stress-response system is involved.
Cortisol is a hormone regulated by the stress-response system. Cortisol levels are typically highest in the morning and fall gradually throughout the day.
Stress-induced changes to cortisol production and regulation can lead to a weaker immune system, and increased fat storage in the abdominal region linked to cardiovascular disease and diabetes.
Shakira Franco Suglia, from Harvard School of Public Health and her team, examined the impact of exposure to community violence on physiological markers of stress response in children.
More specifically, they looked at the influence of post-traumatic stress disorder (PSTD) on daily cortisol response among 28 girls and 15 boys aged 7-13. Some of the PSTD symptoms are difficulty with attention or sleep, intrusive thoughts and flashbacks.
Mothers rated their child's exposure to community violence (such as hearing gunshots, witnessing or experiencing shoving, hitting, punching, knife attacks, shootings) and the resulting post-traumatic stress symptoms.
The researchers also collected saliva samples from the children four times a day over three days to measure cortisol production over the course of the day.
They found a link between exposure to community violence and a disruption to the stress pathways in the body.
The higher children scored on the stress symptoms, the greater the disruption to their cortisol production pattern and the higher their cortisol levels over the course of the day, especially in the afternoon and evening, said a Harvard release.
The study has been published online in Springer's International Journal of Behavioural Medicine